Core coil having a improved temperature characteristic

ABSTRACT

The temperature characteristics of a core and winding assemblage are improved by including within the magnetic circuit of the core an auxiliary core which is composed of a mixture of magnetic powders of various Curie points, whereby the inductance of the core assemblage remains constant over a wide range of temperature.

United States Patent Kato et al. 1 May 16, 1972 [54] CORE COIL HAVING A IMPROVED TEMPERATURE CHARACTERISTIC References i ed [72] lnventors: Umaki Kato; I-Iisao Nishino, both of UNITED STATES PATENTS Yolmhama Japan 2,730,681 1/1956 Went et al ..336/1 79 x [73] Assignee: Tohoku Metal Industries Limited, 3,255,512 6/1966 Lochner et a1 ....336/83 X Yokohama-shi, Japan 3,068,433 12/1962 Wroblewski et a1. ..336/83 3,028,570 4/1962 Taylor ..336/179 X [221 Flledi 1970 3,195,086 7/1965 Taylor ..336/1 79 x [21] Appl. No.: 8,042

Primary Examiner-Thomas J. Kozma Related U.S. Application Data Attorney-Kurt Kelman [63] Continuationin-part of Ser. No. 786,080, Dec. 23, [57] ABSTRACT 1968, abandoned.

The temperature characteristics of a core and winding assem- [30] Foreign A lication Priority Data blage are improved by including within the magnetic circuit of I the core an auxiliary core which is composed of a mixture of Dec. 22, 1967 Japan ..42/82091 magnetic powders f various C i points, whereby the inductance of the core assemblage remains constant over a wide [52] U.S. Cl ..336/l79, 336/83, 336/212 range f temperature [51] Int. Cl. ..H0lt' 15/16 Field of Search ..336/83, 212, 179, 233

8 Claims, 8 Drawing Figures 'Pmnted Ma 16,197z v 3,663,913

5 Sheets-Sheet 1 III all

FIG.3 3

INVENTORS. UMAKI KATO 8: HISAO NISHINO AGENT 5 Sheets-Sheet 5 INVENTORS. UMAK'I K'ATO a HISAO NISHINO AG ENT 5 Sheets-Sheet 4 40C soc 60C T IN VEN TORS.

UMAKI KATO 8|. HISAO NISHINO AGENT Patented May 16, 1972 Y 3,663,913

5 Sheets-Sheet .5

INVENTORS. UMAKI KATO 8| HISAO NISHINO AGENT CORE COIL HAVING A IMPROVED TEMPERATURE CI-IARACTERISTIC This is a continuation-in-part of our copending application Ser. No. 786,080, filed Dec. 23, 1968, now abandoned.

This invention relates to improved magnetic cores for coil windings, and more particularly to cores having inductances which vary in a linear manner over a wide range of temperature.

Generally, the inductance of a magnetic core used with coil windings will vary with temperature, the change in inductance in almost all instances being non-linear over large temperature changes, and being linear only within small changes in temperature.

However, in electronic equipment used in computers, communications, radar and the like, wherein oscillators, filters and the like must operate within closely defined limits, it is imperative that the inductance of the magnetic cores be either constant or vary at a predictable linear rate over a wide range of temperature.

It is an object of this invention to provide a magnetic core for use with a coil which has an inductance which remains constant over a wide range of temperature.

It is another object of this invention to provide a magnetic core for use with a coil which has an inductance which varies linearly over a wide range of temperatures.

It is still another object of this invention to provide a magnetic core for use with a coil which has an inductance which is either constant or varies linearly over a wide range of temperature that is economical to manufacture.

These and further objects and advantages of the present invention are achieved, in general, through the use of an auxiliary core composed of magnetic material whose Curie temperature, the temperature above which the molecular forces of magnetism of paramagnetic bodies cease to exist, is lower than that of the magnetic material of the core, the auxiliary core being arranged in series with the magnetic circuit of the core in some instances, and in parallel with the magnetic circuit of the core in other instances.

The novel features that are considered characteristic of this invention are set forthwith particularity in the appended claims. The invention itself, however, both as to its organization and method of operation, as well as additional objects and advantages thereof, will best be understood from the following description when read in connection with the accompanying drawing wherein:

FIG. 1 is a cross-sectional view in perspective of an E-type core and associated winding in accordance with the principles of this invention;

FIG. 2 is a cross-sectional view in perspective of a pot-type core and associated winding in accordance with the principles of this invention;

FIG. 3 is a cross-sectional view in perspective of a ring-type core and associated winding in accordance with the principles of this invention;

FIG. 4 is a partial sectional view in perspective of a rod-type core and associated winding in accordance with the principles of this invention; and

FIGS. 5 through 8 graphically compare variations of inductance, in percent, with temperature of cores which are modified in accordance with the principles of this invention with cores which are not modified in accordance with the principles of this invention.

Similar reference numerals represent similar throughout the several views of the drawing.

While different shapes and configurations of cores and associated coils are illustrated, the similar parts of the various coil assemblages are designated by the same reference numeral.

parts Referring to FIG. 1, there is illustrated a cross sectional per- 70 spective view of an E-type of core and winding in accordance with the principles of this invention. An E-type of core 1 composed of magnetic material supports a coil 2 which fills up completely the window of the core. The center leg of the E- type core is cut short a predetermined amount and an auxiliary core 3 is positioned within the space provided. The auxiliary core 3 is made of magnetic material whose Curie temperature is lower than the Curie temperature of the magnetic material of which the E-type core is made.

Referring to FIG. 2, there is illustrated a cross-sectional view in perspective of a pot-type core and associated winding in accordance with the principles of this invention. A pot-type of core 1 composed of magnetic material supports a coil 2 which fills up the window of the core. The center leg of the pot-type core is cut short a predetermined amount and an auxiliary core 3 is positioned within the space provided. The auxiliary core 3 is made of magnetic material whose Curie temperature is lower than'the curie temperature of the magnetic material of which the pot-type core is made.

In the embodiments illustrated in FIGS. 1 and 2, the auxiliary core 3 is shown as being in the center leg. It is to be understood that the auxiliary core 3 may also be positioned in one or both of the outer legs; or, the auxiliary core 3 may be positioned in each of the legs.

Referring to FIG. 3, there is illustrated a ring-type core and associated winding. A ring-type core 1 supports an auxiliary core 3 and a winding 2 which is positioned around both the core 1 and the auxiliary core 3.

Referring now to FIG. 4, there is illustrated a rod-type core and associated winding. A rod-type core 1 supports a winding 2, an auxiliary core 3 positioned around the core 1 and the winding 2. The Curie temperatures of the auxiliary cores 3 are again lower than the Curie temperature of the cores 1.

In FIGS. 1 and 2, the auxiliary core 3 is in series in the magnetic circuit of the core. In FIGS. 3 and 4, the auxiliary core 3 is in parallel in the magnetic circuit of the core.

Referring specifically to the embodiment of FIG. 2, a core 1 of IEC type 26 l6 composed of Mn Zn ferrite having a e of 250 and a Curie point or temperature of 170 C. has a temperature characteristic represented by curve 1 of FIG. 5. The combining of an auxiliary core 3 having a thickness of 30;; with the conventional core 1, as illustrated in the embodiment of FIG. 2, causes a change of the temperature characteristics of the assemblage, as shown by curve 2 of FIG. 5. In this assemblage, the auxiliary core was composed of 2-gram adhesive and 1.5 gram Mn Zn ferrite powder, the powder being a mixture of powders of various Curie points as follows:

Curie Point of Powder C.) Ratio in weight 5 2 l 0 3 -l 5 5 20 7 25 I0 30 15 35 20 40 35 where the radius of the particles=9;t; and the total weight equals 1.5 grams.

In determining the characteristics of the core, the coil 2 had turns, and carried 1 ma at lKI-Iz. A Maxwell bridge was used as the measuring apparatus.

Referring again to the embodiment of FIG. 2, a core 1 of IEC type 26l6 composed of Mn Zn ferrite having an re of 250 and a Curie point of 168 C. has a temperature characteristic represented by curve 1 of FIG. 6. The combining of an auxiliary core 3 having a thickness of 40p. with the conventional core 1, as illustrated in the embodiment of FIG. 2, causes a change of the temperature characteristics of the assemblage, as shown by curve 2 of FIG. 6. In this assemblage,

the auxiliary core was composed of -2-gram adhesive and 1.5

Curie Point of Powder C.) Ratio in weight 60 O 40 20 l0 --IO 30 en UIUIUI where the radius of the particles -j-7p.; and the total weight equals 1.5 grams.

The conditions under which the characteristics of the core were determined were the same as those of the first noted example.

Referring still again to the embodiment of FIG. 2, a core 1 of IEC type 26-16 composed of Mn Zn ferrite, having an e of 250 and a Curie point of 168 C. has a temperature characteristic represented by curve 1 of FIG. 7. The combining of an auxiliary core 3 having a thickness of 40 y. with the conventional core 1, as illustrated in the embodiment of FIG. 2, causes a change of the temperature characteristics of the assemblage, as shown by curve 2 of FIG. 7. In this assemblage, the auxiliary core was composed of 2-gram adhesive and 1.5 gram Mn Zn ferrite powder, the powder being a mixture of powders of various Curie points as follows:

Curie Point of Powder C.) Ratio in weight obtained by using auxiliary cores composed of powders having I different Curie points. In a similar manner, the assemblages of FIGS. 1, 3 and 4 can provide cores having characteristics which vary from the characteristics of the core 1 by a desired amount to provide a core assemblage having improved temperature characteristics.

Obviously many modifications and variations of the present invention are possible in the light of the above teaching. It is therefore, to be understood that the invention may be practiced otherwise than as specifically described herein.

What is claimed:

1. The combination of a main magnetic core, a winding coupled to said main magnetic core, and a substantially non-magnetized auxiliary core which is comprised of a mixture of magnetic powders, each powder in the mixture having a diflerent Curie temperature, at least one of said Curie temperatures falling within the normal operating temperature range of the combination, said auxiliary core being coupled to the magnetic circuit of said main magnetic core, whereby the inductance of the combination remains essentially constant over a wide range of temperatures.

2. The combination of claim 1, wherein the Curie temperatures of said magnetic powders are less than the Curie temperature of the main magnetic core.

3. The combination of claim 2, wherein the auxiliary core is coupled in series with the magnetic circuit of the main magnetic core.

4. The combination of claim 2, wherein the auxiliary core is coupled in parallel with the magnetic circuit of the main magnetic core.

5. The combination of claim 2, wherein the auxiliary core is coupled to the main magnetic core.

6. The combination of claim 5, wherein the main magnetic core comprises two sections and the auxiliary core is interposed between said sections of the main ma netic core.

7. The combination of claim 5, wherein t e auxiliary core IS coupled to one surface of the main magnetic core.

8. The combination of claim 5, wherein the main magnetic core is positioned within the auxiliary core. 

1. The combination of a main magnetic core, a winding coupled to said main magnetic core, and a substantially non-magnetized auxiliary core which is comprised of a mixture of magnetic powders, each powder in the mixture having a different Curie temperature, at least one of said Curie temperatures falling within the normal operating temperature range of the combination, said auxiliary core being coupled to the magnetic circuit of said main magnetic core, whereby the inductance of the combination remains essentially constant over a wide range of temperatures.
 2. The combination of claim 1, wherein the Curie temperatures of said magnetic powders are less than the Curie temperature of the main magnetic core.
 3. The combination of claim 2, wherein the auxiliary core is coupled in series with the magnetic circuit of the main magnetic core.
 4. The combination of claim 2, wherein the auxiliary core is coupled in parallel with the magnetic circuit of the main magnetic core.
 5. The combination of claim 2, Wherein the auxiliary core is coupled to the main magnetic core.
 6. The combination of claim 5, wherein the main magnetic core comprises two sections and the auxiliary core is interposed between said sections of the main magnetic core.
 7. The combination of claim 5, wherein the auxiliary core is coupled to one surface of the main magnetic core.
 8. The combination of claim 5, wherein the main magnetic core is positioned within the auxiliary core. 